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Commitments and contingencies - Allowance for Credit Losses on Unfunded Commitments (Details) - USD ($) $ in Thousands | 12 Months Ended |
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Dec. 31, 2020 | Jan. 01, 2020
Commitments and Contingencies [Roll Forward] |  |
Balance at beginning of period | $ 31,139 |
Balance at end of period | 170,389 |
Unfunded Commitments |  |
Commitments and Contingencies [Roll Forward] |  |
Balance at beginning of period | 0 |
Impact of CECL adoption on provision for credit losses on unfunded commitments |  | $ 2,947
Increase in provision for credit losses from unfunded commitments acquired in business combination | 10,499 |
Provision for credit losses on unfunded commitments | 2,932 |
Balance at end of period | $ 16,378 |

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